JavaScript Examples
Dave Braunschweig
Strings
// This program demonstrates string functions. main(); function main() { var str = "Hello"; output("string: " + str); output("string.toLowerCase(): " + str.toLowerCase()); output("string.toUpperCase(): " + str.toUpperCase()); output("string.indexOf('e'): " + str.indexOf('e')); output("string.length: " + str.length); output("string.replace('H', 'j'): " + str.replace('H', 'j')); output("string(substring(2,4): " + str.substring(2, 4)); output("string.trim(): " + str.trim()); var name = "Bob"; var value = 123.456; output(`string.format(): ${name} earned $${value.toFixed(2)}`); } function output(text) { if (typeof document === 'object') { document.write(text); } else if (typeof console === 'object') { console.log(text); } else { print(text); } }
Output
string: Hello string..toLowerCase(): hello string.toUpperCase(): HELLO string.indexOf('e'): 1 string.length: 5 string.replace('H', 'j'): jello string(substring(2,4): ll string.trim(): Hello string.format(): Bob earned $123.46
Files
Note: For security reasons, JavaScript in a browser requires the user to select the file to be processed. This example is based on node.js rather than browser-based JavaScript.
// This program demonstrates reading a text file with exception handling. const fs = require('fs'); main(); function main() { const filename = "temperature.txt"; readFile(filename); } function readFile(filename) { try { const text = fs.readFileSync( filename, {encoding:"utf8"}); const lines = text.split("\n"); for (const line of lines) { console.log(line); } } catch (exception) { console.log(exception) } }
Output
Celsius,Fahrenheit 0,32 10,50 20,68 ... 80,176 90,194 100,212